Scalable silicon-based optical fibre has solar-cell capabilities

A silicon-based optical fibre with solar-cell capabilities has been developed that has been shown to be scalable to many metres in length.

The research is claimed to facilitate the possibility of weaving together solar-cell silicon wires to create flexible, curved or twisted solar fabrics.

The findings by an international team of chemists, physicists, and engineers, led by John Badding, a professor of chemistry at Penn State University, will be published by the journal Advanced Materials.

The team’s new findings are said to build on earlier work addressing the challenge of merging optical fibres with electronic chips — silicon-based integrated circuits that serve as the building blocks for most semiconductor electronic devices such as solar cells, computers, and mobile phones.

Rather than merge a flat chip with a round optical fibre, the team found a way to build a new kind of optical fibre with its own integrated electronic component, thereby bypassing the need to integrate fibre optics with chips.

According to a statement, the team did this by using high-pressure chemistry techniques to deposit semiconducting materials directly, layer by layer, into tiny holes in optical fibres.

Now, in its new research, the team members have used the same high-pressure chemistry techniques to make a fibre out of crystalline silicon semiconductor materials that can function as a solar cell.

‘Our goal is to extend high-performance electronic and solar-cell function to longer lengths and to more flexible forms. We already have made metres-long fibres but, in principle, our team’s new method could be used to create bendable silicon solar-cell fibres of more than 10m in length,’ Badding said. ‘Long… solar cells give us the potential to do something we couldn’t really do before: we can take the silicon fibres and weave them together into a fabric with a wide range of applications such as power generation, battery charging, chemical sensing, and biomedical devices.’

Badding explained that one of the major limitations of portable electronics such as smartphones and iPads is short battery life and that solar-boosted batteries could help solve this problem.

‘A solar cell is usually made from a glass or plastic substrate onto which hydrogenated amorphous silicon has been grown,’ Badding said. ‘Such a solar cell is created using an expensive piece of equipment called a PECVD reactor and the end result is something flat with little flexibility. But woven… solar cells would be lightweight, flexible configurations that are portable, foldable and even wearable.’

This material could then be connected to electronic devices to power them and charge their batteries. ‘The military especially is interested in designing wearable power sources for soldiers in the field,’ Badding added.

The team members believe that another advantage of flexibility in solar-cell materials is the possibility of collecting light energy at various angles.

‘A typical solar cell has only one flat surface,’ Badding said. ‘But a flexible, curved solar-cell fabric would not be as dependent upon where the light is coming from or where the sun is in the horizon and the time of day.’

Pier J A Sazio of Southampton University and one of the team’s leaders added: ‘Another intriguing property of these silicon-fibre devices is that as they are so compact, they can have a very fast response to visible laser light. In fact, we fabricated photodetectors with a bandwidth of more than 1.8GHz.’

The research was funded by the National Science Foundation, Penn State’s Materials Research Institute Nano Fabrication Network, and the EPSRC.

A cross-sectional image of the new silicon-based optical fibre with solar-cell capabilities. Shown are the layers — labelled n+, i, and p+ — that have been deposited inside the pore of the fibre. Credit: Badding lab, Penn State

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